Color television



Dec. 28, 1948.

G. c. SYZIKILAI' COLOR mmvrsxon 3 Sheets-Sheet 1 Filed March 31, 1945 LCZ/P til/EL 5114: urn m2 110 & 119

- INVENTOR GEORGE C Jz/A LA/ ATTORNEY Dec. 28, 1948. 2,457,415

G. C. SZlKLAl COLOR TELEVISION Filed March 51, 1945 3 Sheets-Sheet 2 U VERTICAL DE/Z [CT/0N INVENTOR GEO/e 5 6. JZ/KL/l/ ATTORNEY Dec. 28, 1948. s. c. SZIKLAI 5 Shee'ts-Sheet 3 INVENTOR m ATTORNEY JLILIL sy/vc 103 K L 6 k G 2 t Patented Dec. 28, 1948 COLOR TELEVISION George C. Sziklai, Princeton, N. .L, asslgnor to Radio Corporation of America,

of Delaware a corporation Application March 31, 1945, Serial No. 585,907 2 Claims. (Cl. 1785.4)

The present invention relates to systems for the reproduction of television images in natural colors, and more particularly to a novel system and arrangement or light filters foruse in such or analogous systems.

It has been the practice in many instances in television systems for transmitting video signals representative of the diiferent color components of the scanned images to utilize color filters at both transmitters and receivers to obtain these color'separation signals. These filters are frequently mounted on discs, wheels, or drums which are rotated in synchronism with one another at the transmitter and receiver and so moved that the light of the image passes through diiTerent component color filter sections at the field scanning rate.

In modern television receivers, space is at a premium and the inactive sections of a rotary component color separation filter occupy a space which is not otherwise useful and which, therefore, necessitates a cabinet larger than the cabinet which would be provided for a similar receiver operating only to present single color images. Also, a motor which is employed to drive the disc or other type component color separation filter is relatively large and expensive and is space consuming, as well as being noisy.

In accordance with the present invention, a novel color filtering arrangement which is compact, substantially noiseless, and positive in its operation is provided. The improved filters of the invention which cooperate in practice to expose successive images ior direct viewing or projection on a screen are in the form of gratings having alternate transparent and light modifying lines or strips. These gratings are operated successively and sequentially and cyclically at rates necessary for reproducing colored images by compact means which are or may be substantially self-contained.

The primary object of the present invention is to provide a novel component color separation filter arrangement for a color television system. Another object is to provide a novel arrangement for operating a series of members, such as light filtering members, in a desired sequence and at a predetermined cyclic rate.

A further object is to provide a novel light controlling device for transmitting light of a predetermined color.

A still further object is to provide a novel component color separation filter system which accomplishes selective filtering by vibratory movement of its elements.

Other and more specific objects of the invention will become apparent from a consideration of the following specification and claims in connection with the accompanying drawings illustrating one preferred form of the invention in which:

Fig. 1 is a plan view, partially in section, illustrating a color filter arrangement in accordance with the invention;

Fig. 2 is a fragmentary view in end elevation of the device of Fig. 1;

Fig. 3 is a fragmentary view showing a detail of a filter element adjusting means;

Fig. 4 is a schematic showing of a circuit suitable for providing sequential and cyclic operation of the filter elements;

Fig. 5 is a schematic showing of a modified operating system;

Fig. 6 shows a series of curves referred to in describing the operation of Fig. 5; and

Fig. 7 shows fragmentarily a modification of Fig. 1.

Figs. 1 and 2 of the drawings show the general arrangement of the filter device as well as the details of the component color separation filter units. The entire filter device will be referred to hereinafter by reference character l0, and upon reference to Fig. 2, it will be seen that this unit may be mounted on the base member I2 of a television cabinet ll which is fragmentarily shown in section. The base member l2, just referred to, may be the bottom of the cabinet or it may be the top of a television chassis or a sub base especially provided for the purpose of supporting the filter device In. The television apparatus includes an image producing source which is most commonly a cathode ray tube It having a fluorescent screen or target l8 scanned by a cathode ray beam 20 moving to produce a predetermined scanning pattern or raster on the fluorescent screen or target [8. The longest dimension of the raster will, in general, be shorter than the diameter of the screen l8 so that separate masking means (not shown) may be positioned in front of the target area of the tube IS.

The unit ill, to be described in detail, may be arranged to mask the unused portion of" the end of the tube l8 by providing any one or all of the filter members to be described with an opaque border outlining the scanned raster of the tube target.

The number of component color separation filters of the device ill will, of course, be determined by the color system employed. Three filters 2 I, 22, and 23 are shown :by way of example 3 as usable in a tricolor system. In the tricolor arrangement selected byway of example, these three filter sections are usually the component colors blue, green;'and red of an additive color system, and they are exposed in a consistent predetermined sequence. It will be understood that the choice of colors and the-exposure sequence of the colors will depend entirely upon the color system to be used at the television studio and transmitter and in the receiver l4. The equipment for sequential scanning of the original image in different colors is not disclosed herein, but it will be understood that any system of scanning may be employed for developing a series of video or image signals to be applied at receiving points to appropriate electrode or electrodes of the tube l6 in timed relationship to the presentation of the individual filters 2| to 23 before the target area viewed or the mosaic of the camera tube of a transmitter.

An arrangement for effecting television scanning at the transmitter end of a tricolor system camera tube is used to resolve the light image into signals for transmission is shown in Patent No. 2,297,524, granted to E. I. Anderson on September 29, 1942, which may be regarded as illustrative of one form of transmitter system. It will be understood that the device ID of the invention to be described in detail may be applied at the transmitter if color filters are to be placed before the camera tube. .3

The filter device l0 includes a member 26 having alternate opaque and transparent or translucent lines or strips 28 and 29, respectively. The filter members 2| to 23 are provided with light transmitting strips 3| alternating with light modifying strips 32. In the system selected by way of illustration, the strips 32 for each of the members 2i to 23 transmit light of one only of the selected component colors, member 2| having blue light transmitting strips, member 22 having green light transmitting strips, and the member 23 having red light transmitting strips. These members 2| to 23 and 26 are superimposed. as suggested by Fig. 1 of the drawings. the spacing being greatly exaggerated for the sake of convenience of illustration. It will be understood that the members 2|, 22, 23, and 26 are substantially in contact with each other and are in the nature of self-supporting films of light weight, such as, for example, the type employed in photography. Sheets of cellulose nitrate or cellulose acetate are well adapted for the purpose as well as other transparent materials. These members may also be constructed of glass if it is so desired. The color strips may be provided on the surface of each of the members or in the body thereof, although it is sufllcient for the purpose of the invention if these strips are merely printed on the surface of the members in appropriate transparent colors.

The entire device i0, including the filter members, is carried by a frame 34 having a supporting connection, as mentioned previously, with the base l2 or another appropriate part of the television receiver i4. The movable filter members 2| to 23 are all mounted in the frame 34 in a similar manner so that the description of the mounting means for the member 23 will suffice for all. This member is square or rectangular (for example, substantially the shape of the scanned raster) and is provided atone edge with an electrical conductor 38 which may be cemented to the body of the sheet constituting this wherein a storage type cathode 'ray television I member by employing an adhesive or softening the body of the member with a solvent such as amyl acetate. The conductor may also be molded within the body of the member. Spring members 38 and 38 are attached to the frame 34, and their free ends are secured to the conductor 36 or they may be formed as a unit with the conductor 36. These springs exert tension on the member 23 by tending to move it toward the left of the cabinet as viewed in Fig. 2. A wire 4| is connected to the top edge of the member 23 and includes an elastic portion in the form of a spring 42. The portion of the wire 4| or a separate wire beyond the spring 42 is anchored to a rod 44 which is rotatably mounted in a bearing or bearings 46 as is best shown in Fig. 3 of the drawings. Rotation of the rod 44 provides a convenlent means for adjusting the tension on the wire 4|. It will be understood that several wires may be spaced vertically along the edge of the member 23, each being secured as shown to the rod 44 so that they are all simultaneously adjustable. A micrometer screw 49 having threaded engagement in a support 5| is in contact with a radial lever 63 secured to the rod 44 so as to, provide for micrometric adjustment of the tension applied to the wire or wires 4|. The spring or springs 42 act in opposition to the springs 38 and 38.. In order conveniently to provide definite limits of movement for the member 23, a stop plate 56 is supported in any suitable manner, for example by the frame 34, so that the wire or wires 4| may pass through a perforation or perforations 58. A stop which may be in the form of a head 59 sets one limit of movement of the member 23, and a second bead 6i sets the other limit of movement. In a like manner the wires 62 and 83 for the members 2| and 22 are provided with stop beads 66 and 61. Other stop beads 68 and 69 set the other limit to the range of movement of the members 2| and 22 respectively.

In the unit l0, and by way of example, the member 26 is' mounted in a stationary position although for certain purposes it may be the movable member. This member 26 may be conveniently positioned by means of wires 1| secured to the stop plate 56 and by members (not shown) similar to the springs 38 and 39 but of a more rigid nature.

Movement is selectively imparted to any one of the members 2| to 23 by securing electrical conductors at their ends in a manner already explained in connection with the conductor 36 for the member 23. Conductors l3 and 14 are therefore secured at or adjacent the edge of the members 2| and 22. A magnet, preferably an electromagnet, having a core member 16 and an energizing winding 11, provides a strong magdevice, such as speed and degree of response, will be readily realized. 7

Operating currents may be provided to the conductors in any desired manner, for example by a rotating commutator (not shown) driven by a synchronous motor operating in step with the vertical deflection of the cathode ray beam. The

method of synchronizing the motor is shown and is fully described in the above referred to patent to Anderson. Moreover, an electronic commutator of the kind disclosed in a patent to Schumard, No. 2,146,862, granted February 14, 1939, and a patent to Roys et al., No. 2,089,430. ranted August 10, 1937, may be employed to successively energize the conductors or the filter members. The stop beads 6|, 60, and 69 will be located at a fixed distance from the stop plate 56 when the several conductors are de-energized if a commutator-distributor is employed. Also, the light modifying strips 34 of the member 22 will normally be out of register with the strips 29 of the member 26.

Fig. 4 of the drawings shows an arrangement for operating the several members which are represented diagrammatically by the conductors 36, I3, and I4. A countercircuit 82, such as is described on page 588 of Theory and Application of Electron Tubes by H. J. Reich, published 1939, is fed with pulses from the vertical deflection circuits of the receiver I4 or other suitable synchronizing source to produce a potential increase in a series of steps designated B, G, and R, these symbols corresponding for convenience to the color designations of the several filter members. A suitable type of countercircuit is also shown in a United States Patent No. 2,113,011, granted to E. L. C. White, April 5, 1938.

Referring now to Fig. 1 of the drawings, it will be seen that the color strips 84 of the member 22 are positioned opposite the transparent sections 29 of the member 26 when the conductor I4 is de-energized. This corresponds to the portion marked G of the countercircuit output which is or may be of substantially zero magnitude. The next member in the series to operate is the member 23 and this operation may be accomplished by providing a tube 83 which passes plate current when the potential on its grid 86 reaches the potential value R of the countercircuit output. Member 23 is assumed in this example to have red strips. This potential will cause a current sufficient strength to flow through the conductor 14 to draw the member 22 to the left as viewed on Fig. 2, thereby bringing the colored sections 84 of this member opposite the opaque sections 28 of the member 26. The stop bead 60 holds the member 22 in its ineffective position throughout the remaining operating cycle.

During the previously described operation of the members 22 and 23, the member 2| is maintained stationary by a blocking bias on the grid 38 of a tube 89. A tube 92 serves as an amplifier to invert the counteroutput wave and this inverted wave'is applied to the grid 93 of a tube 94. When the negative signal applied to the grid 93 reaches the value B in the negative sense, the tube 94 will be cut off thereby raising the grid to a positive potential such that the tube 89 conducts causing movement of the member 2|. At this time also, the plate current through the tube 03 is increased resulting in additional movement of the member 23 to its inactive position. The double spacing of the stop bead 6| permits this additional movement. When the countercircuit output falls to zero, the members 2|, 22, and 23 are restored, and the member 22 is active.

Fig. of the drawing shows a modification of the arrangement of Fig. 4 in which a controlled multivibrator is employed for operating the members 23 and 2| at the proper time with respect to the operation of the member 22 as in Fig. 4.

ductors 36, I3, and I4 of Fig. 1.

The member 22 is operated'by its conductor I4 directly from the step wave I02 provided by a countercircuit I03. The countercircuit is applied to a clipper stage I04 which selects the highest potential portion or the wave I02 as a square wave I06 which is differentiated by a difierentiating circuit I01. Both the positive and negative pulses are available after difierentiating, as 1 indicated at I09, to control a multivibrator IIO comprising tubes HI and H2. The pulses I03 occur at a time determined by the steep portions H4 and H6 of the counteroutput and reversal of operation of tubes 0 and H2 of the multi-- vibrator occurs at proper time to select members 23 and 2| for operation. During the zero portion of the counteroutput when the member 22 is to be exposed, the tubes H8 and H9 are rendered inoperative by applying a blocking bias to their grids I20 and I2I. This bias is obtained in the proper sense from the amplifier tube Ill and the tube I23. Correct cycling of the multivibrator may be insured by observing the image for color and operating a key I42 momentarily until proper color values appear.

To review the operation of the arrangement of Fig. 5 briefly, when the output of the countercircuit I03 is at its minimum level, the conductor I4 is de-energized and the colored strips 84 are exposed. At this time the multivibrator will have operated previously to prepare the tube II9 for operation. However, at this time the tube is cut on by its grid I2I, the bias'level for accomplishing this being indicated at I26 in Fig. 5 of the drawings, When the output of the multivibrator rises above the level I26, tube II9 becomes conductive since the blocking bias is removed from its grid I20, and the member 23 is operated while at the same time the member 22 moves to the limit determined by the location of its stop bead 68. When the counteroutput rises to the level B, a differentiated pulse reverses the conductivity of the multivibrator tubes III and H2 operating the member 2| by energizing the tube H8. The colored strips in this member are exposed until the tube H8 is again cut off by the tubes I22 and I23, as explained previously. Tube H8 is prepared again by reversal of the multivibrator at a point II6 of the repeating wave I02.

Fig. 7 of the drawing illustrates a modification of the arrangement of Fig. 1 in which a member I28, corresponding to the member .26 of Fig. 1, is provided with alternate opaque and transparent or translucent strips I29 and I3I. A movable member I34 is provided with colored strips I36 to I39 which are slanted with respect to the strips I29 and I3I. Either one of the members I28 or I34 may be provided with means for moving them, for example by a conductor such as the con- In a preferred arrangement, the member I28 is stationary, provided that the color strips are slanted as shown. With the slanted strips a sawtooth wave may be applied to the operating conductor since, in that case, the color will follow the scanning and persistence of the tube.

In view ofthe foregoing complete description of the arrangement of Figs. 1 to 3, it is believed that a separate description of the operation of the arrangement of Fig. 7 is unnecessary.

The device I0 as described herewith follows a very wide range of frequencies (20 to 10,000 cycles or more) and a very short return time may be obtained. While a certain amount of light is lost due to the filter members, this is offset by the simplicity of the device in construction, op-

.eration. and accessories. the members of Figs. 1 and 7 are mounted verti- The strips of each of cally for the standard type of picture raster and the strips of Fig. 1 for a receiver or camera tube, having a 7 inch diameter raster for example, may be on the order of .014 inches in width, this'figure 'being given solely by way of example. 'This also a appliesto the strips I29 and 13! of Fig. 7.

Various modifications in the invention shown and described herein by way of example are pose sible and as an example, the members of Figs. 1 and 7 may be operated mechanically by cams on a shaft or the like driven by a synchronous motor although this arrangement is not preferred. Having now described the invention, what is claimed and desired to be secured by Letters Patent is the following:

1. Color television apparatus comprising a cathode ray tube having a target area, scanning means associated with said tube to scan said target area successively and cyclically, a light filter device substantially equal in area to the target area of said tube scanned by said scanning means, said filter device being interposed in a light path which includes the target area of said tube, said light filter device comprising a plurality of filter members of a shape in outline corresponding to the outline of the scanned target area of the tube, each member having light transmitting strips alternating with light modifying strips, the light modifying strips of. one of said members serving to block the passage of light, and means for shifting said remaining members sequentially in a predetermined order in timed relationship with the successive scannings of the said target area.

2. Color television apparatus comprising a cathode ray tube having a target area, scanning means associated with said tube to scan said target area successively and cyclically,-a light filter device interposed in a light path which includes the target area of said tube, a member of said device having alternate opaque and light transmitting strips, a second member having a plurality 01 light filtering strips arranged in consistent succession, and means to cause relative movement between said members for bringing the light modifying strips of said second member successively in register with the light transmitting strips oi said first named member.

GEORGE C. SZIKLAI.

REFERENCES CITED The following references are of record in th file of this patent:

UNITED s'rn'ms PATENTS Number Name Date 947,490 Gwozdz Jan. 25, 1910 2,285,262 Fess et a1. June 2, 1942 2,297,524 Anderson Sept. 29, 1942 2,303,196 Busse Nov. 24, 1942 2,313,224 Cawein Mar. 9, 1943 2,389,979 Huffnagle Nov. 27, 1945 FOREIGN PATENTS Number Country Date 555,670 Great Britain Sept. 2, 1943 

